This application claims the benefit of Korean Application No. 2001-5939, filed Feb. 7, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a functional film, and more particularly, to a functional film having adjustable optical and electrical properties.
2. Description of the Related Art
A functional film having electrical conductivity while minimizing reflectance of external light has a variety of applications. These applications include sun glasses, external light shielding glass, UV protective and insulating materials or electromagnetic shielding materials.
The functional film is also used as a black matrix formed between phosphor layers of a color display device, such as a color cathode ray tube. In this context, the functional film absorbs the external light and the light scattered from adjacent phosphor layer patterns. If the reflectance of the external light of a screen of a display device increases, a visible image becomes blurred. Since the external light is reflected mainly at a black matrix of the screen, attempts to improve luminance and contrast by increasing the absorbance of the black matrix surrounding pixels of the display device have been continuously made. Thus, a black matrix is fabricated to have a laminated film structure using chromium, and more specifically, using a film consisting of a chromium layer and a chromium oxide layer. In order to further increase the absorptivity of the black matrix, carbon may be added to the chromium oxide layer.
U.S. Pat. No. 5,976,639 discloses a method of forming a black matrix for a liquid crystal display using a laminated film consisting of a transition layer and a metal layer on the inner surface of a display panel. According to this patent, the laminated film has a transition layer in which the content of one constituent element, such as Cr, W, Ta, Ti, Fe, Ni or Mo, increases approximately between 0.5% to 20% per 100 xc3x85 in the incident direction of external light. The transition layer may further include a constituent element such as oxygen, nitrogen or carbon. The metal element is desirably chromium. The transition layer is disposed between a low metal layer and a high metal layer. The content of metal elements of the high metal layer is in the range of 50% to 100% by weight. The content of metal elements of the low metal layer is in the range of 10% to 50% by weight. The low metal layer is not the essential constituent from the viewpoint of the function of a black matrix.
The black matrix is manufactured by a reactive sputtering method in which a metal (chromium) target is placed on a magnetron cathode in a vacuum chamber, a first gas is introduced into the chamber for magnetron discharging, and a second gas, (i.e., a reactive gas such as oxygen or nitrogen to react with the sputter metal elements) is introduced into the chamber. Sputtering is performed at an atmosphere in which the partial pressure of the reactive gas gradually decreases in the moving direction of a transparent substrate.
However, in the black matrix and preparation method thereof described in U.S. Pat. No. 5,976,639, materials that are environmentally detrimental such as chromium, are used, and the deposition should be performed at a reactive atmosphere. Also, during formation of the transition layer and the metal layer in the laminated film, the composition and thickness of each layer must be strictly controlled so as to make the manufacturing process complex.
To solve the above and other problems, it is an object of the present invention to provide a functional film having excellent mechanical, optical and electrical properties by using a mixture of a nontoxic metal other than chromium and a dielectric material.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To accomplish the above and other objects, a functional film according to an embodiment of the invention includes a transition layer having a first constituent and a second constituent having gradual content gradients varying according to a thickness of the functional film, the first constituent being at least one dielectric material selected from the group consisting of SiOx (x greater than 1), MgF2, CaF2, Al2O3, SnO2, In2O3 and indium tin oxide (ITO), and the second constituent being at least one material selected from the group consisting of iron (Fe), cobalt (Co), titanium (Ti), vanadium (V), aluminium (Al), silver (Ag), silicon (Si), germanium (Ge), yttrium (Y), zinc (Zn), zirconium (Zr), tungsten (W) and tantalum (Ta).
According to an aspect of the invention, the gradual content gradients are distributed such that a refractive index gradually increases or decreases in an incident direction of external light according to the thickness of the functional film.
According to another aspect of the invention, the gradual content gradients are distributed such that a light absorption efficiency gradually increases in the incident direction of the external light according to the thickness of the functional film.
According to still another aspect of the invention, the gradual content gradients are distributed such that an electrical conductivity gradually increases or decreases by varying a content of the second constituent according to the thickness of the functional film.
According to yet another aspect of the invention, the gradual content gradients are distributed such that a content of the first constituent gradually decreases and the content of the second constituent gradually increases in the incident direction of the external light according to the thickness of the functional film.
According to another embodiment of the present invention, the functional film is deposited on a substrate having a refractive index difference of less than or equal to 0.5 at an interface between the substrate and the functional film.
According to still another embodiment of the present invention, the functional film further includes a dielectric layer formed of at least one dielectric material selected from the group consisting of SiOx (x greater than 1), MgF2, CaF2, Al2O3, SnO2, In2O3 and ITO.
According to a further aspect of the invention, the dielectric layer is deposited between the substrate and the transition layer and contacts the substrate.
According to a still further aspect of the invention, a difference in a refractive index between the dielectric layer and the substrate is less than or equal to 0.5.
According to a further embodiment of the present invention, the functional film further includes a conductive layer including at least one metal element selected from the group consisting of iron (Fe), cobalt (Co), titanium (Ti), vanadium (V), aluminium (Al), silver (Ag), germanium (Ge), yttrium (Y), zinc (Zn), zirconium (Zr), tungsten (W), and tantalum (Ta).
According to an additional aspect of the invention, the formation location of the conductive layer is formed on a face opposite an interface between the functional film and the substrate in the cases where the functional film is used in the fields requiring electrical conductivity characteristics, the second constituent is silicon, and the Si content increases according to the thickness of the film.
According to a still yet another embodiment of the present invention, the functional film further includes a dielectric layer and a conductive layer comprising at least one metal element selected from the group consisting of iron (Fe), cobalt (Co), titanium (Ti), vanadium (V), aluminium (Al), silver (Ag), germanium (Ge), yttrium (Y), zinc (Zn), zirconium (Zr), tungsten (W) and tantalum (Ta), where the conductive layer is formed at a face opposite the interface between the transition layer and the dielectric layer.